Description: Apo-1 (Fas/CD95) is a 45 kD type I transmembrane protein belonging to the TNF receptor family. A subgroup of this receptor family called ‘death receptors’ contain 3-4 cysteine-rich repeats in the extracellular portion and a cystoplasmic motif called the ‘death domain’, which is responsible for the transduction of the death signal. The death domain associates with FADD/MORT, which in turn connects to aspartate-specific proteases (Caspases) that are implicated as mediators of most types of apoptotic cell death (6-9).